The present invention relates in general to an ink jet recording apparatus for ejecting charged fine particle-containing ink to record an image using electrostatic field, and more particularly to an ink jet recording apparatus configured to narrow a particle diameter distribution of the fine particles to prevent degradation of image quality of a recorded image.
An electrostatic ink jet recording system uses charged fine particle-containing ink, and a predetermined drive voltage is applied to control electrodes provided in the vicinities of ink nozzles (through holes) of an ink jet head based on image data to control ejection of ink droplets by utilizing electrostatic forces. As a result, an image corresponding to the image data is recorded on a recording medium.
In JP 3,288,279 B for example, there is disclosed an ink jet recording apparatus including: a control substrate disposed so as to face a recording medium, the control substrate including an insulating support substrate, and first and second control electrodes disposed on both sides of the insulating support substrate, respectively, the control substrate having at least one through hole formed so as to extend completely through the first and second control electrodes and the insulating support substrate; ink supply means for supplying ink to the through hole of the control substrate, the ink supply means having a porous member disposed so as to contact the second control electrode; and signal voltage application means for applying a signal voltage corresponding to an image signal across the first and second control electrodes.
In this ink jet recording apparatus, a bias voltage is applied across the first and second control electrodes, and the signal voltage superposed on the bias voltage is applied across the first and second control electrodes. As a result, positively charged colored particles move to an ink surface within the through hole. When an amount of colored particles becomes equal to or more than a given amount, an electrostatic force acting on the ink surface increases beyond an ink surface tension, with the result that the electrostatic force breaks the ink surface to eject the charged colored particles with a high concentration.
Then, in the above-mentioned ink jet recording apparatus, the charged colored particles with a high concentration are ejected in such a manner, whereby an image having less bleeding can be formed, fine recording picture dots can be formed on a recording medium, an image having high resolution can be readily recorded, and moreover an image having high resolution can be formed irrespective of recording media.
However, in the ink jet recording apparatus disclosed in JP 3,288,279 B, as will be described later, the concentration of the charged colored particles may become unstable, or an ejection state of the charged colored particles may become unstable. In particular, when the continuous recording is carried out, this tendency becomes remarkable.